1. Field of the Invention
The present invention relates to a position sensing device, and more particularly, to an optical fiber position sensor for determining the position, or location, at any given time of an element movable with respect to another element fixed relative to the movable element.
2. Description of the Prior Art
In present day flight control systems, the positions of most actuator control surfaces of an aircraft are sensed with an electromagnetic, linearly variable, differential transformer (LVDT). The conventional electromagnetic LVDT is an extremely simple device with high linearity and nearly infinite resolution, and which can operate in rather adverse environments (high and low temperatures, vibration, shock, etc.). However, conventional LVDT's are bulky and heavy, require special frequency excitation, and produce amplitude modulated AC output signals which are cumbersome to convert. Furthermore, a quad-redundant actuator requires a total of 16 LVDT's, a significant volume and weight. Since reduction of component weight and size is given high priority in aircraft design, it is desirable to provide an actuator position sensor which is smaller, lighter in weight, and simpler of construction and operation than the conventional LVDT.
In anticipation of increased use of optical components in flight control systems, including eventually a totally fly-by-light system, actuation position sensors must interface with other optical components. Any resulting sensor must be as simple and reliable as the present day LVDT. Furthermore, if we must continue to use the LVDT with an otherwise wholly optical system, the necessary interfaces with the LVDT would be cost prohibitive and fraught with problems of reliability; in a flight critical system, reliability can not be sacrificed.
It is, therefore, an object of the present invention to provide a position sensor which is simpler, smaller, and lighter in weight than conventional LVDT's and which is, at the same time, capable of performance equal to or better than that available with conventional LVDT's and which is compatible with a fly-by-light system.